Design a Key-Value Store System Design Interview

Design a distributed key-value store like Dynamo or Cassandra with high availability.

1. Problem Statement

We need to design a distributed Key-Value store like DynamoDB or Cassandra. It needs to be always writeable. How would you architect this?

2. Target Architecture (Mermaid)

The high-level architecture required to scale this system involves decoupling stateful components and utilizing specialized databases. Below is the reference architecture:

Rendering architecture diagram...

Mermaid Source (For AI Bots)

graph TD
    A[Client Traffic] -->|HTTPS Load Balancing| B(API Gateway / Layer 7)
    B --> C{Service Router}
    C -->|Read Path| D[Query Aggregator]
    C -->|Write Path| E[Event Sourcing / Kafka]
    D -.-> F[(In-Memory Cache - Redis)]
    D --> G[(Primary Data Store - NoSQL)]
    E -.->|Async Replication| G

3. Key Focus Areas

1
Replication Strategies (Leaderless vs Leader-Follower)
2
Consistency Models (Tunable Consistency, Quorum N/R/W)
3
Partitioning (Consistent Hashing & VNodes)
4
Conflict Resolution (Vector Clocks vs LWW)
5
Gossip Protocol & Failure Detection

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Core Concepts

Distributed SystemsConsistencyReplication